Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Site Activity Active Carbon Coverage And Methane Selectivity Of Cobalt Fischer Tropsch Catalysts Microform Effects Of Catalyst Composition And Reaction Conditions
Download Site Activity Active Carbon Coverage And Methane Selectivity Of Cobalt Fischer Tropsch Catalysts Microform Effects Of Catalyst Composition And Reaction Conditions full books in PDF, epub, and Kindle. Read online Site Activity Active Carbon Coverage And Methane Selectivity Of Cobalt Fischer Tropsch Catalysts Microform Effects Of Catalyst Composition And Reaction Conditions ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Author :Christopher Jason Bertole Publisher :National Library of Canada = Bibliothèque nationale du Canada ISBN 13 :9780612691001 Total Pages :490 pages Book Rating :4.6/5 (91 download)
Book Synopsis Site-activity, Active Carbon Coverage and Methane Selectivity of Cobalt Fischer-Tropsch Catalysts [microform] : Effects of Catalyst Composition and Reaction Conditions by : Christopher Jason Bertole
Download or read book Site-activity, Active Carbon Coverage and Methane Selectivity of Cobalt Fischer-Tropsch Catalysts [microform] : Effects of Catalyst Composition and Reaction Conditions written by Christopher Jason Bertole and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2002 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Investigation of Intrinsic Activity of Cobalt and Iron Based Fischer-Tropsch Catalysts Using Transient Kinetic Methods by : Alexandre Antônio Bento Carvalho
Download or read book Investigation of Intrinsic Activity of Cobalt and Iron Based Fischer-Tropsch Catalysts Using Transient Kinetic Methods written by Alexandre Antônio Bento Carvalho and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work exposed in this manuscript concerns the study of the intrinsic activity and localization of active sites in cobalt and iron based catalysts using a combination of transient kinetic methods such as SSITKA, extended physicochemical characterization and catalytic tests under quasi steady state conditions. Promotion of iron catalysts with metals used for soldering (Bi and Pb) results a remarkable increase in the light olefin production rate with the possibility to conduct Fischer-Tropsch synthesis at very mild reaction conditions (low pressure) and even at atmospheric pressure. Transient kinetic experiments showed facilitation of CO dissociation in the presence of promoters by scavenging O atoms from iron carbide. Cobalt catalyst supported by mordenite zeolite presented higher value of SSITKA rate constant. Localization of cobalt active sites in bifunctional cobalt-zeolite catalysts has a major impact on the reaction rate and in particular on the hydrocarbon selectivity. A proximity between the cobalt active site and Bronsted active sites was found to be a key parameter to obtain higher selectivity and yield of isomerized hydrocarbons. SSITKA combined with catalyst characterization revealed that carbon deposition and cobalt nanoparticle agglomeration were responsible for the deactivation of silica supported cobalt catalysts. Catalyst rejuvenation in hydrogen lessened the amounts of deposited carbon species and partially released the most active sites of carbon monoxide dissociative adsorption and stronger sites of carbon monoxide reversible adsorption.
Download or read book Fossil Energy Update written by and published by . This book was released on 1984 with total page 844 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Fischer-Tropsch Reaction Over Ti-Modified Cobalt Catalysts by : Andrew Ronald Raub
Download or read book The Fischer-Tropsch Reaction Over Ti-Modified Cobalt Catalysts written by Andrew Ronald Raub and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents research done to investigate the promoter effects of small amounts of titanium oxides (TiOx) on unsupported cobalt metal catalysts for the atmospheric pressure Fischer-Tropsch (CO+H2) reaction. It is known that cobalt catalysts with TiO2 supports can have their performance for the Fischer-Tropsch reaction enhanced due to interactions between cobalt metal and the support. Small TiOx species can migrate onto the surface of metal particles during reductive treatment, termed the "strong metal-support interaction" (SMSI). Interactions between TiOx species and the cobalt metal are expected to influence its catalytic behavior. Techniques were developed to create unsupported cobalt metal catalysts dosed with controlled amounts of TiOx via oxalate precursors. By eliminating the presence of a supporting material, interactions between cobalt metal and TiOx could be focused on. This is the first time that TiOx alone has been studied as a promoter species in controlled amounts over an unsupported cobalt catalyst for the atmospheric pressure CO+H2 reaction.Steady state and chemical transient kinetic (CTK) reaction studies revealed that very small amounts of Ti (~1-2 atom%, relative to cobalt) induce changes in the catalyst structure and product selectivity. The addition of TiOx to the cobalt resulted in increased selectivity toward alkenes and suppression of CH4 and C2H6 that persisted over long reaction times. When TiOx is present, CTK measurements revealed the presence of surface intermediates that are absent over pure cobalt and react with different kinetics to form chain lengthened hydrocarbons. Estimated carbon amounts on the catalyst surfaces showed ~3 carbon atoms/cobalt metal site for pure cobalt catalysts, and ~5-6 carbon atoms/cobalt metal site for Ti-modified cobalt catalysts. General observations made about formation and decay behavior for hydrocarbon products during CTK studies were in good agreement with those obtained for similar work done on CoMgO and CoMnOx catalysts. Suggestions for the direction of future work on Ti-modified cobalt catalysts are made at the end of this dissertation.Some effort has also been spent on using methyl formate, which can be considered a liquid form of syngas, to produce chain lengthened hydrocarbons using CoMnTi catalysts. This ternary catalyst composition was selected due to its industrial relevance. Some transient kinetic studies were performed but turned out challenging to interpret due to the complexity of parallel decomposition pathways for methyl formate. In view of the complexity of the CoMnTi catalyst composition, it was deemed important to first focus on the CoTi case as a prerequisite for studying more complicated catalyst formulations.
Book Synopsis Iron and Cobalt Catalysts by : Wilson D. Shafer
Download or read book Iron and Cobalt Catalysts written by Wilson D. Shafer and published by MDPI. This book was released on 2020-06-23 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the turn of the last century when the field of catalysis was born, iron and cobalt have been key players in numerous catalysis processes. These metals, due to their ability to activate CO and CH, haev a major economic impact worldwide. Several industrial processes and synthetic routes use these metals: biomass-to-liquids (BTL), coal-to-liquids (CTL), natural gas-to-liquids (GTL), water-gas-shift, alcohol synthesis, alcohol steam reforming, polymerization processes, cross-coupling reactions, and photocatalyst activated reactions. A vast number of materials are produced from these processes, including oil, lubricants, waxes, diesel and jet fuels, hydrogen (e.g., fuel cell applications), gasoline, rubbers, plastics, alcohols, pharmaceuticals, agrochemicals, feed-stock chemicals, and other alternative materials. However, given the true complexities of the variables involved in these processes, many key mechanistic issues are still not fully defined or understood. This Special Issue of Catalysis will be a collaborative effort to combine current catalysis research on these metals from experimental and theoretical perspectives on both heterogeneous and homogeneous catalysts. We welcome contributions from the catalysis community on catalyst characterization, kinetics, reaction mechanism, reactor development, theoretical modeling, and surface science.
Book Synopsis Metal Oxide Promotion of Cobalt-Based Fischer-Tropsch Synthesis Catalysts by : Gregory Robert Johnson
Download or read book Metal Oxide Promotion of Cobalt-Based Fischer-Tropsch Synthesis Catalysts written by Gregory Robert Johnson and published by . This book was released on 2015 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthetic fuel production by means of Fischer-Tropsch synthesis (FTS) involves the catalytic hydrogenation of CO over Co-based catalysts. Often, these catalysts incorporate performance-enhancing additives known as promoters. Although not catalytically active for FTS by themselves, promoters can alter the structural and electronic properties of the active Co metal so as to improve catalyst activity, selectivity, or stability. Elements that form metal oxides have been studied for their ability to increase CO consumption rates and shift the product distribution toward higher molecular weight. Despite several decades of study of such elements, there remains limited understanding of the connections between these promotional effects and element properties. Accordingly, this dissertation focuses on clarifying the chemical basis for the effects of metal oxide promotion and making connections to periodic trends. To understand the importance of physical contact between the promoter and the Co, the influence of Co-Mn spatial association on the magnitude of Mn promotional effects was investigated. Elemental maps obtained by STEM-EDS revealed that different catalyst pretreatment methods could control how closely associated the promoter and Co were at the nanoscale. By relating these results to catalytic reaction data, it was determined that higher extents of contact between the two elements were correlated with higher selectivities toward C5+ hydrocarbons. This work was extended to the elements Ce, Gd, La, and Zr, which are among the most commonly studied metal oxide-forming promoters. The presence of the promoter element suppressed methane formation and increased the FTS chain propagation probability, but the sensitivity of these effects toward promoter loading was different for each element. Elements that deposited preferentially onto the Co nanoparticles led to rapid shifts in the product distribution as the promoter loading increased, whereas elements that dispersed over the entire catalyst surface resulted in more gradual changes. For all promoters, the product selectivities became insensitive to loading when the loading reached a quantity nearly equivalent to that which would form a half monolayer of the promoter on the Co nanoparticle surface. These trends are characteristic of the formation of active sites along the interface between the Co and the promoter that exhibit improved product selectivity. Structurally, the oxidation states and local coordination environments of the promoters were consistent with highly dispersed oxides. No evidence for the formation of bimetallic alloys or large promoter-containing crystallites was detected by either X-ray absorption spectroscopy or X-ray diffraction. These data suggest that small promoter oxide moieties decorate the surface of the Co metal nanoparticles so as to form metal-metal oxide interfaces. Under this model, the promotional effects increase in magnitude as the fraction of Co active sites that are adjacent to the promoter increases. When the Co surface is sufficiently covered by the promoter so that the fraction of active sites that are along the perimeter of the promoter moieties is nearly unity, the catalyst performance ceases to improve as a function of promoter loading. Guided by this reasoning, the catalytic properties of the promoted catalysts were investigated using samples in which the fraction of sites that were promoted was near unity. Measurements of reaction kinetics were conducted to assess the impact of metal oxide promotion on the rate parameters governing FTS. The rates of CO consumption for both unpromoted and metal oxide-promoted catalysts followed a Langmuir-Hinshelwood rate law for which H-assisted CO dissociation is assumed to be the rate determining step. Each promoter increased the apparent rate constant and the CO adsorption constant that appear within the rate law. Thus, metal oxide promotion appears both to facilitate the cleavage of the C-O bond and to enhance the extent of CO adsorption onto the catalyst. This finding was reinforced by CO temperature programmed desorption experiments and an evaluation of the effects of Mn promotion on the rate of CO disproportionation. Owing to the appearance of the CO adsorption constant in the numerator and denominator of the rate law, it is possible for promoted catalysts to have both higher and lower turnover frequencies than unpromoted catalysts depending on the chosen operating pressure. As a consequence, an optimal promoter can be found for maximizing the turnover frequency at a given operating pressure. However, product selectivity, which is largely determined by the availability of adsorbed H, is invariably improved by a higher CO adsorption constant because it decreases the ratio of adsorbed H to CO on the Co surface. Strong correlations between catalyst performance and the Lewis acidity of the promoter oxide suggest that Lewis acid-base interactions between the promoter and the adsorbed CO are the cause for the observed metal oxide promotional effects. Much of the experimental data presented in this work favors the hypothesis that CO can interact simultaneously with Co through the C atom and with the promoter cation through the O atom. These chemical interactions, in which the promoter serves as a Lewis acid, weaken the bond between C and O. Experimental evidence for this effect was observed in the lower activation barrier for CO hydrogenation over the ZrO2-promoted catalysts and the appearance of adsorbed carbonyl species on the MnO-promoted catalyst with severely redshifted C-O stretching frequencies measured by in situ infrared spectroscopy. These results provide insight into the chemical mechanism by which metal oxides affect the reaction and identify Lewis acidity of the promoter as the relevant descriptor for quantitatively predicting metal oxide-based promotional effects over Co FTS catalysts.
Book Synopsis Catalytic Conversion of Carbon Monoxide and Methane Over Metal and Metal Oxide Catalysts by : Wenchi Liu
Download or read book Catalytic Conversion of Carbon Monoxide and Methane Over Metal and Metal Oxide Catalysts written by Wenchi Liu and published by . This book was released on 2018 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysis is of vital importance in a wide range of areas including energy processing and chemical production. Catalytic conversion of C1 sources such as carbon monoxide and methane to make hydrocarbon fuels and oxygenated products has far reaching implications especially in the context of the gradual depletion of crude oil resource and the potential surge in the natural gas production in the coming decades. The control over reaction activity and selectivity for the conversion CO and CH4 in the Fischer–Tropsch synthesis and oxidative coupling of methane (OCM) have received tremendous attention and have been proved challenging. This dissertation focuses on the catalytic conversion of CO (Fischer–Tropsch synthesis) using supported cobalt based bimetallic nanoparticle model catalysts and the oxidative coupling of methane with noble metal promoted metal oxide catalysts. Using colloidal synthesis, a series of cobalt based bimetallic nanoparticles Co–M (M = Mn, Ru, Rh, and Re) with well-defined sizes, shapes, and compositions were obtained. Detailed synthesis procedures were presented and key synthetic parameters were discussed. The as-synthesized nanoparticles were subjected to extensive in-situ X-ray spectroscopy studies using ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and X-ray absorption spectroscopy (XAS) under catalytic relevant conditions. Composition wise, the results indicate the surface concentration of Co on the as-synthesized Co–M bimetallic particles is slightly less than the bulk atomic Co %. While oxidation treatment led to a slight increase of the surface Co, major effect was seen after the reduction treatment where surface segregation of the second metal resulted in a drastic decrease of the surface Co content. The effect is more pronounced at elevated reduction temperatures. Under reaction conditions, the surface compositions remained similar to those after the reduction treatment at high temperatures. Among the bimetallics tested, the Co–Mn system is relatively less susceptible to surface reconstructions induced by oxidation and reduction treatments. In addition, the reducibility of Co was also shown to be modified depending on the second metal present and Re was proved to be most efficient in leading to a facile reduction of Co. Catalytic performance of the bimetallic catalysts supported on mesoporous silica MCF–17 indicates a positive effect in the catalytic activity for Co–Rh and Co–Mn systems, while Co–Re and Co–Cu showed decreased activity. Less pronounced promotion effect of the second metal on the product distribution was observed with only a slight increase in the selectivity towards C5+ products. The selectivities for CH4 and C5+ of the various Co–M bimetallic catalysts generally resemble those of pure Co catalysts. Although in extremely low selectivity, alcohols were also formed with Co–Rh and Co–Cu bimetallic catalysts. The appearance of longer chain alcohol such as propanol, which was not present for pure Co catalysts, is an evidence for potential synergistic promotion. For oxidative coupling of methane (OCM), the promotion effect of noble metals (Pt, Ir, and Rh) on the performance of MnxOy-Na2WO4/MCF–17 catalysts was investigated. The introduction of noble metals had little effect on the surface area and phase composition of the original catalyst but led to a more reduced nature of the surface oxide species. Catalytic study revealed an enhanced selectivity towards both C2 and C3 hydrocarbons as compared to the undoped MnxOy-Na2WO4/MCF–17 catalyst in the order of Rh-doped > Ir-doped > Pt-doped samples together with a lower olefin to paraffin ratio. A more optimized strength of interaction between the carbon intermediates and the catalyst surface was suggested, which in combination with the improved reducibility of Mn and W species are believed to be responsible for the improved performance. In addition, monodispersed leaf-like manganese–tungsten–oxide (Mn–W–Ox) nanoparticles and hydroxylated hexagonal boron nitride (h-BN) were synthesized and used as novel catalysts in OCM reaction. Preliminary results indicate that the MCF–17 supported Mn–W–Ox nanoparticle catalyst showed a CH4 conversion of 5.4% and C2 selectivity of 42% with good stability over time. On the other hand, hydroxylated h-BN exhibited good activity (~20% CH4 conversion) with moderate selectivity towards C2 hydrocarbons (20%–30%). However, the hydroxylated h-BN catalysts faced serious deactivation, which was not eliminated by lowering the reaction temperature or the oxygen concentration in the reaction gas feed.
Book Synopsis Cobalt Fischer-Tropsch Catalysts Having Improved Selectivity by :
Download or read book Cobalt Fischer-Tropsch Catalysts Having Improved Selectivity written by and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A cobalt Fischer-Tropsch catalyst having an improved steam treated, acid extracted LZ-210 support is taught. The new catalyst system demonstrates improved product selectivity at Fischer-Tropsch reaction conditions evidenced by lower methane production, higher C.sub. 5.sup.+ yield and increased olefin production.
Download or read book Fischer-Tropsch Synthesis written by and published by . This book was released on 2016 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of ammonia in syngas on the performance of various supported cobalt catalysts (i.e., Al2O3, TiO2 and SiO2) was investigated during Fischer-Tropsch synthesis (FTS) using a continuously stirred tank reactor (CSTR). The addition of ammonia (10 ppmv NH3) caused a significant deactivation for all supported cobalt catalysts, but the rate of deactivation was higher for the silica-supported catalysts relative to the alumina and titania-supported catalysts used in this work. Ammonia addition had a positive effect on product selectivity (i.e., lower light gas products and higher C5+) for alumina and titania-supported catalysts compared to ammonia free conditions, whereas, the addition of ammonia increased lighter hydrocarbon (C1-C4) products and decreased higher hydrocarbon (C5+) selectivity compared to ammonia-free synthesis conditions for the silica-supported catalyst. For alumina and titania-supported catalysts, the activity almost recovered with mild in-situ hydrogen treatment of the ammonia exposed catalysts. For the silica-supported catalyst, the loss of activity is somewhat irreversible (i.e., cannot be regained after the mild hydrogen treatment). Addition of ammonia led to a significant loss in BET surface area and changes in pore diameter (consistent with pore collapse of a fraction of pores into the microporous range as described in the literature), as well as formation of catalytically inactive cobalt support compounds for the silica-supported catalyst. On the other hand, the pore characteristics of alumina and titania-supported catalysts were not significantly changed. In conclusion, XANES results of the ammonia exposed silica-supported catalysts further confirm the formation of cobalt-support compounds (cobalt silicates).
Book Synopsis Development of a Stable Cobalt-ruthenium Fischer-Tropsch Catalyst by :
Download or read book Development of a Stable Cobalt-ruthenium Fischer-Tropsch Catalyst written by and published by . This book was released on 1991 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this contract is to examine the relationship between catalytic properties and the function of cobalt Fischer-Tropsch catalysts and to apply this fundamental knowledge to the development of a stable cobalt-based catalyst with a low methane-plus-ethane selectivity for use in slurry reactors. An experimental cobalt catalyst 585R2723 was tested three times in the fixed-bed reactor. The objective of the tests was to identify suitable testing conditions for screening catalyst. The?-alumina was determined to be a suitable diluent medium for controlling the catalyst bed temperature close to the inlet temperature. With 13 g of catalyst and 155 g of diluent, the catalyst maximum temperature were within 2°C from the inlet temperatures. As a result of this work, 210°C and 21 atm were shown to result in low methane selectivity and were used as initial conditions in the catalyst screening test. Ethane, which along with methane is undesirable, is typically produced with low selectivity and follows the same trend as methane. Other work reported here indicated that methane selectivity increases with increasing temperature but is not excessively high at 230°C. Consequently, the catalyst screening test should include an evaluation of the catalyst performance at 230°C. During Run 67, the increase in temperature from 210°C to 230°C was initiated at 30 hours on-stream.
Book Synopsis L'état des entreprises 2013 by : Dauphine Recherches en management (Paris)
Download or read book L'état des entreprises 2013 written by Dauphine Recherches en management (Paris) and published by . This book was released on 2012-11-22 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: La 4e de couv. indique : "Pour la cinquième année consécutive. DRM propose dans ce Repères un regard pluriel sur le monde des entreprises en mettant l'accent sur les enjeux et tendances actuels. Parmi les sujets traités cette année, des questions variées liées à l'actualité des organisations sur le marketing du non-marchand, la question de la reconnaissance au travail, les pratiques de l'interculturel dans les firmes multinationales, les modèles de finance islamique, la gestion de l'absentéisme au travail. Des références bibliographiques sont fournies à la fin de chaque contribution et l'ouvrage s'achève par une chronologie des événements récents. L'ensemble fournit une synthèse actualisée, un véritable état annuel des entreprises."
Book Synopsis Understanding Noble Metal Addition in Cobalt Fischer Tropsch Catalysts by : Kari Marie Cook
Download or read book Understanding Noble Metal Addition in Cobalt Fischer Tropsch Catalysts written by Kari Marie Cook and published by . This book was released on 2012 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of noble metal (NM) promotion and deposition order (co-deposition of NM with the final Co deposition [co-dep] or sequential deposition of NM after Co deposition [seq-dep]) on surface area, pore size, metal retention, crystallite size, noble metal distribution and bonding in Co Fischer Tropsch (FT) catalysts were studied as were the resulting Co reducibility and Fischer Tropsch activity/selectivity properties. Catalysts containing nominally 25wt% Co with either 0.3 wt% Ru, 0.58 wt% Pt, 0.55wt% Re, or no NM on a La-stabilized-Al2O3 support were prepared by wet deposition. The Co, Pt, and Re were uniformly dispersed, but Ru distribution and retention were problematic and deposition-order dependent--85% was lost with co-dep, but it was uniformly distributed while 54% was lost with seq-dep and it was concentrated at the pellet edge. The co-dep catalysts all have smaller reduced Co crystallite size than their corresponding seq-dep catalysts. The average crystallite diameters for all 3 co-dep catalysts are between 4.1 and 4.3nm and ~90% of the crystallites are 6nm. XAFS measurements showed that after reduction at 360oC, Pt is bonded with Co even with mild calcination between the final Co and the Pt deposition. On the other hand, neither Ru nor Re formed direct bonds with Co. Ru remained in a separate metal phase after reduction even at low loadings. Re remained as Re2O7 and still promoted Co reduction well (e.g. 42% reduced to Co metal compared to none for the unpromoted catalyst). By all measures of reducibility (TPR, EOR, H2 uptake), all NM promoted catalysts were more reducible than the unpromoted catalyst. The co-dep catalysts have lower TPR peak temperatures, but lower extents of reduction than their corresponding seq-dep catalysts. The NM type effect on overall extent of reduction trend was Co/Pt-seqCo/Re-seq>Co/Ru-seq=Co/Pt-co>Co/Re-co>Co/Ru-co>Co. The Co/Pt-co catalyst was the most active of all the catalysts both on rate per mass and per site basis. The co-dep catalysts were all more active than the corresponding sequentially deposited catalysts. The co-dep Pt and Re catalyst activity is greater due to higher activity per site, while co-dep Ru activity is greater due to a higher abundance of active sites.
Book Synopsis Kinetics and Selectivity in Fischer-Tropsch Synthesis on a Cobalt Catalyst by : Bent Sarup
Download or read book Kinetics and Selectivity in Fischer-Tropsch Synthesis on a Cobalt Catalyst written by Bent Sarup and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Preparation of Active, Stable Supported Iron Catalysts and Deactivation by Carbon of Cobalt Catalysts for Fischer-Tropsch Synthesis by : Kamyar Keyvanloo
Download or read book Preparation of Active, Stable Supported Iron Catalysts and Deactivation by Carbon of Cobalt Catalysts for Fischer-Tropsch Synthesis written by Kamyar Keyvanloo and published by . This book was released on 2014 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second half of this dissertation investigates the effects of operating conditions including the partial pressures of CO and H2 and temperature on the deactivation by carbon of 25 wt% Co/ 0.25 wt% Pt/Al2O3 catalyst. It also reports the kinetics of the main FT reaction on this catalyst. As temperature increases, the H2 and CO orders for the main reaction (in the absence of deactivation) become more positive and more negative, respectively. A new mechanism was proposed to account for the inhibition effect of CO at high reaction temperatures, which includes H-assisted dissociation of CO to C* and OH*. Further, twelve samples of the CoPt/Al2O3 catalyst were tested over a period of 800 hours and XCO
Book Synopsis Effect of Cobalt and Zinc Precursor Loading on the Catalyst Activity of Fischertropsch Synthesis by : Nadia Aida Che Mustapa
Download or read book Effect of Cobalt and Zinc Precursor Loading on the Catalyst Activity of Fischertropsch Synthesis written by Nadia Aida Che Mustapa and published by . This book was released on 2012 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: Five samples of Co-Zn/SBA-15 catalysts were prepared using wet impregnation method with different composition of cobalt loading (5, 10 and 15 wt % Co) and zinc loading (5, 10 and 15 wt % Zn) and were investigated with respect to physical and chemical properties as well influence on activity and selectivity for conversion of H2/CO2 synthesis gas. The catalysts were tested by using Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), N2 Adsorption Analysis (BET) and Thermogravimetric Analyzer (TGA). The feed gas of CO2 instead of CO also had been considered that contributed to product selectivity since cobalt catalyst do not exhibit significantly in Water Gas Shift (WGS) activity and CO2 neither formed nor produced during Fischer Tropsch (FT) synthesis with cobalt catalyst and H2/CO. An investigation of catalytic CO2 hydrogenation into high quality fuels and valuable hydrocarbons was carried out in a glass borosilicate reactor. The operating condition for catalytic testing is at 220 °C and 1 bar using H2/CO2 feed ratios of 3:1. Selectivity of products was depending upon the amount of metal loading constituent as well as the syngas mixture that used. It was found that higher metal loading with optimized promoter loading was the best catalyst for Fischer Tropsch synthesis. It is experimentally found that from the result of gas chromatograph, the conversion of CO2 and product selectivities were calculated. The most efficient catalyst for Ficher Tropsch synthesis is 15% Co/10% Zn-SBA-15. This result was proven by the characteristic of catalyst which is the existance functional groups of cobalt oxides, Si-O-Si, Si-CH3, zinc oxide, OH band, Si-C, and others, higher intensity that indicates higher cobalt dispersion, possess large surface area as well as pore size, small weight loses that indicate thermal stability and having large number of catalyst particles attaching closely with one another that make it more effective during FT process.
Book Synopsis Technology Development for Iron and Cobalt Fischer-Tropsch Catalysts by :
Download or read book Technology Development for Iron and Cobalt Fischer-Tropsch Catalysts written by and published by . This book was released on 1999 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impact of deuterium on the Fischer-Tropsch (FT) synthesis was studied with a precipitated iron catalyst in the slurry phase. Deuterium has been used by several research groups to better understand the mechanism of CO hydrogenation. Inverse (k{sub H}/k{sub D} 1), normal (k{sub H}/k{sub D} 1) and no isotope effect (k{sub H}/k{sub D} = 1) have been reported. The conflicting results are thought to arise because rate of reaction is a combination of kinetic and equilibrium factors. In summary, the presence of boron produced only minor changes on the properties of the cobalt catalyst. In earlier studies, it was shown that the presence of boron made the catalyst less susceptible to poisoning by sulfur. Steady-state supercritical Fischer-Tropsch synthesis was studied in the work using a fixed-bed reactor and an unpromoted Co/SiO2 catalyst. This serves as the baseline for promoted catalyst studies. A pentane-hexane mixture was used as the supercritical solvent. Overall reactor pressure, syngas partial pressure and contact time were kept constant to obtain a valid comparison of the impact of solvent density in the catalytic activity and selectivity. Three different partial pressures of the mixture were chosen based on the density-pressure curve in order to investigate the pressure tuning effect to Fischer-Tropsch synthesis near critical region.
Book Synopsis Deactivation Modeling of Cobalt Fischer-Tropsch Catalysts in Different Reactor Configurations by : Majid Sadeqzadeh
Download or read book Deactivation Modeling of Cobalt Fischer-Tropsch Catalysts in Different Reactor Configurations written by Majid Sadeqzadeh and published by . This book was released on 2012 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalyst deactivation remains a major challenge in Fischer-Tropsch synthesis; as it reduces the catalyst lifetime as well as its productivity. Deactivation can be attributed to certain mechanisms according to the literature. Sintering is proposed in this work to be responsible for the initial deactivation whereas coking is suggested to be the main cause of long-term deactivation. The final objective of this thesis is to develop the mechanistic models which could predict the extent of catalyst deactivation with time. In the first step, the change in the catalyst physico-chemical properties with time on stream is considered. A three-step sintering model is proposed which involves the effect of water acceleration through the formation of surface cobalt oxide layer. This mechanism allows correlating the crystallites growth with certain operating conditions especially the H2O/H2 molar ratio inside the reactor. We have also developed a mechanism for the active site poisoning by carbon deposition for the long-term deactivation. This mechanism helps to evaluate the change in the active sites coverage with time as well the CO, H2, and H2O mole fractions. The two microscopic models are then integrated in the reactor models in order to correlate the change in the catalytic activity with the catalyst properties. We have developed the models dedicated to fixed bed and slurry reactors. The effect of operating conditions on the crystallite size, active sites fraction, and conversion is considered by the simulations. The models are then employed in the laboratory scale reactors to fit the experimental data and to optimize the deactivation constants.
![Download Site-activity, Active Carbon Coverage and Methane Selectivity of Cobalt Fischer-Tropsch Catalysts [microform] : Effects of Catalyst Composition and Reaction Conditions PDF Online Free](https://books.google.com/books/content/images/frontcover/-SWAtgAACAAJ?fife=w200-h370)
